Growing up I always wore glasses so I virtually never wore safety glasses. I "could see it coming" and could close my eyes fast enough to not have to worry about it. Plus, if you're smart with your directional placement of sparks AND keep your head out of the grinding path by at least 10° you're usually pretty safe.
Once I started wearing contacts I almost always wear safety glasses. The problem is that you must realize that most crap that gets in your eyes falls out of your eyebrows/hair and/or rolls down your face into your eyes... then when you blink you do the damage.
However, in the last few years I've noticed that i can't close my eyes as fast. I try to religiously wear safety glasses... still tend not to when using the dremel tool but everything else I've always got them on. Sometimes I forget I have them on.
The trick to making yourself wear them is to find good glasses-type ones with good side shields. They aren't as much of a chore to wear. If you find ones that fit you good they protect very well (especially large lenses).
I hate wearing goggles, they make you so uncomfortable that you tend not to wear them.